Poacher knife as it is won't work.
Counterjungle is more effective when the enemy doesn't know you are invading. Whe nyou buy poacher you give him a huge sign saying "I'm gonna invade you. I sacrificed my farming and my gank potential to do this! ". Why don't you merge rangers and poacher together. If the counter jungle isn't farming he will be able to farm his jungle anyway and if he wants to counter jungle he has the tools to do so without using a mega phone to warn the other jungler.
